Field of the Invention
Because in modern communications technology there is an increasing demand for the transmission of video information, such as still and moving images in video telephone applications, or the representation of high-resolution graphics in modern data processing systems, the significance of transmission and switching techniques for high data transmission rates (over 100 megabits per second) is increasing. One known data transmission method for high data speeds is known as the asynchronous transfer mode (ATM). At present, data transmission on the basis of the asynchronous transfer mode makes a variable transmission bit rate of up to 622 megabits per second (Mbit/s) possible.
From the data sheet entitled “MOS INTEGRATED CIRCUIT μPD98410” published by NEC Corporation, 1997, Document No. S12624EJ1V0DS00 (1st edition), a large-scale-integrated ATM switching chip with a processing speed of 1.2 gigabits per second (Gbit/s) is known, which allows the addressing of a plurality of subscriber-oriented interfaces via a high-frequency ATM-specific bus interface (UTOPIA: Universal Test & Operations PHY Interface for ATM).
It has already been proposed that so-called ATM multiplexers be used for connecting subscriber devices to the ATM-specific bus interface of the high-frequency ATM switching chip. In them, a plurality of low-rate connection lines (with a bit transmission rate of 25.6 Mbit/s or 155 Mbit/s, for instance) intended for connecting the subscriber devices are concentrated by an ATM multiplexer on the higher-rate connection line of the high-frequency ATM switching chip (which has a bit transmission rate of 622 Mbit/s, for instance).
In a subscriber device, such as a data processing system, multiple different applications each running simultaneously are typically handled, such as a video telephone application and data forwarding on the basis of the IP (Internet Protocol) for an internet application. These different applications, because of their different needs for individual-application data forwarding, result in different connections between any two subscriber devices. The needs are addressed by an assurance, or so-called service fidelity quality. Here a distinction is made between cell-loss-sensitive and non-cell-loss-sensitive applications. The cell-loss-sensitive applications, data forwarding is effected via real-time-oriented connections, in which the loss of a data cell leads to a sacrifice in the quality of the connection, since because of real-time requirements, for instance, the lost data cell cannot be re-forwarded. In non-cell-loss-sensitive applications, data forwarding is effected via non-real-time-oriented connections, in which the loss of a forwarded data cell can be compensated for by re-forwarding of the lost data cell or of a cohesive succession of data cells (for instance in IP-based data forwarding).
To meet these needs, that is, to assure the “service fidelity quality”, in the context of making a connection, so-called service fidelity parameters are forwarded from the subscriber devices to the controller of an ATM switching system by a standardized signaling method (standardized in: ATM Forum, User Network Interface Specification, Version 4.0). As a result, a constant data transmission rate, often abbreviated as “CBR” (for constant bit rate) in the literature, is furnished for a connection, or real-time-critical data forwarding, often abbreviated as “rt VBR” (for real-time variable bit rate), is assured via a coupling field of the ATM switching system (in accordance with ATM Forum, Traffic Management Specification, Version 4.0).
From the article, “Traffic Management for an ATM Switch with Per-VC Queueing: Concept and Implementation”, IEEE Communications Magazine, January 1998, it is known that large ATM switching systems, to assure the “service fidelity parameter” of a connection, have additional multiplexing units (SMUs, for Statistical Multiplexing Units), which on the basis of the “service fidelity parameters” forwarded control the data forwarding via the coupling field by a special method, in the literature, often called “statistical multiplexing”. Statistics multiplexing dictates buffer storage of the data to be forwarded and thus requires that large memory units be furnished.
To assure the “service fidelity-quality” of connections existing between terminal devices if the agreed-upon “service fidelity parameters” are infringed by some other terminal device, so-called real-time traffic monitoring mechanisms, in the literature, often also called “policing”, are additionally implemented in large ATM switching systems.
In smaller ATM switching systems, furnishing large memory units and implementing complicated real-time traffic monitoring mechanisms, also known as “workgroup switches”, is not commercially feasible, however.